(1) Field of the Invention
The present invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of preserving the integrity of a spin-on polymer gap filling material during planarization of a dielectric layer in the fabrication of integrated circuits.
(2) Description of the Prior Art
The new generation of low dielectric constant organic and inorganic silsesquioxane spin-on polymers have the unique property of thermal reflow that improves the planarity and gap filling characteristics of the interlayer dielectric. The thermal reflow property is more pronounced top of thin metal lines than on wide or large metal features. That is, the spin-on polymer will reflow away from the thin metal lines of less than about 10 microns in width and collect between the lines, but the polymer will remain over the wide metal lines of more than about 10 microns in width. Reflow will also take place at the corners of the wide metal lines. Hence, once the spin-on polymer on the wide metal features is etched away, the current oxide to conventional polyoxide spin-on-glass selectivity for planarization etchback can no longer ensure the preservation of the integrity of the underlying oxide barrier and the thin metal lines. This problem is illustrated in FIGS. 1 and 2.
Referring now more particularly to FIG. 1, there is illustrated a partially completed integrated circuit device. Semiconductor device structures, not shown, may be fabricated in and on the semiconductor substrate 10. Metal lines 20 are formed over insulating layer 11. Titanium nitride anti-reflective coating layer 22 is formed on the metal lines. An oxide 24 is conformally deposited over the pattern of metal lines 20. Spin-on polymer 26 is coated over the oxide layer. The conventional planarization etchback using CHF.sub.3 /CF.sub.4 chemistry has a selectivity of oxide to the spin-on polymer of 1.6:1. As illustrated in FIG. 2, after etchback, the polymer over the wide metal line 31 has been etched away to the underlying oxide. The anti-reflective coating 22 has been etched away over the thin metal lines 33, exposing the metal 20.
Co-pending U.S. patent application Ser. No.08/767,008 (CS96-033) to J. Z. Zheng et al filed on Dec. 16, 1996 teaches a combination anti-reflective coating and polish stop layer to improve gap-filling and planarization of a dielectric layer. U.S. Pat. No. 5,262,348 to Bindal et al shows a method of forming nitride polish stops in the bottom of apertures. U.S. Pat. No. 5,362,669 to Boyd et al teaches forming a polish stop layer in the middle of a wide trench to prevent dishing. U.S. Pat. No. 5,324,690 to Gelatos et al teaches forming a ternary boron nitride film as a polish stop layer. U.S. Pat. No. 5,385,866 to Bartush teaches using an oxidized boron nitride polish stop layer. U.S. Pat. No. 5,246,884 to Jaso et al teaches a CVD diamond or diamond-like carbon polish stop layer.